<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .big{
            overflow: hidden;
            width: 200px;
            border: 2px solid #000;
        }
        .up{
            float: left;
            width: 100px;
            height: 100px;
            background-color: #ccc;
        }
        .down{
            float: left;
            width: 100px;
            height: 100px;
            background-color: #f9d8f8;
        }
    </style>
</head>
<body>
    <!-- 清除浮动 -->
    <div class="big">
        <div class="up"></div>
        <div class="down"></div>
    </div>
</body>
</html>